Generally, surface-enhanced spectroscopy involves spectroscopic analysis of an analyte that is in close proximity to a metallic surface having sub-micron sized topographical features. Under these conditions, the spectroscopic signal may be increased by spatially confining the analyte within range of the electromagnetic fields generated upon excitation of the localized surface plasmon resonance of the metal surface at the topographical features.
A variety of spectroscopic analysis techniques have been shown to benefit from this type of surface effect including: surface-enhanced Raman spectroscopy (SERS), surface plasmon resonance spectroscopy, surface-enhanced infrared spectroscopy, and surface-enhanced sum frequency generation spectroscopy.
Typically, such techniques are conducted by bringing a substance to be analyzed (e.g., a gas, liquid, or solid) in close proximity to the metal layer that is supported on a relatively small area (e.g., 1 cm by 1 cm) substrate. Through this technique the signal of an analyte may be increased in intensity by up to 8 orders of magnitude (or more) depending on conditions, and in some cases may even be sensitive enough to detect even individual molecules.